The invention relates generally to a coupling.
More particularly, the invention relates to a coupling for rotatably connecting a pair of rotary members, e.g., a reel and a drive shaft for the reel.
A known coupling for rotatably connecting a pair of rotary members includes a support for holding the members against relative rotation. The support, which rotates with the members, is provided with a recess designed to receive a complementary portion of one of the members, e.g., a stub shaft of a reel for winding and unwinding lengths of material. An arresting element in the form of a wheel is rotatable with the support and is pivotable between a release position in which the recess is accessible for insertion or removal of a member, and an arrest position in which removal of a member from the recess is prevented. The pivot axis of the arresting wheel extends transverse to the axis of rotation of the support. A positioning element which bridges the support and the arresting wheel in the arrest position of the latter serves to locate the arresting wheel in the arrest position.
A coupling of this type without a positioning element is disclosed in the West German Pat. No. 917 592. This coupling is designed with abutments and openings which insure that, if the coupling begins to rotate while the arresting wheel is in the release position, the arresting wheel is automatically moved to the arrest position.
Another coupling of the above type is known from the West German Pat. No. 31 27 553. The coupling of the patent has a positioning element for locating the arresting wheel in the arrest position, and the positioning element is in the form of a ball which engages the support and the arresting wheel in such position.
A problem arises with conventional couplings when the member accommodated by the recess of the support is heavy and the coupling is rotated 90.degree. from the position it occupies during insertion of the member into the recess. Under such circumstances, the weight of the member is transmitted to the arresting wheel and, if the portion of the member in the recess then undergoes deformation due to the weight of the member, the arresting wheel is biased to the release position. The arresting wheel may be unable to resist the forces acting upon it, even if the arresting wheel is located in the arrest position by means of a ball, and may accordingly pivot to the release position. The tendency of the arresting wheel to move to the release position is increased when the portion of the member in the recess has an edge in engagement with the arresting wheel. In such a situation, the forces exerted by the member are transmitted almost exclusively to the arresting wheel over an extended angle of rotation of the latter.
The positioning ball offers limited resistance to movement of the arresting wheel from the arrest position to the release position in order to allow intentional pivoting of the arresting wheel to the release position as easily as possible.